NIVRKKK

USA

NIVRKKK is a weaker stimulator of the Hsc70 (Heat-shock cognate protein 70) ATPase activity compared with pigeon cytochrome C peptide and FYQLALT, a peptide optimized for binding to Hsc70. FYQLALT effectively blocks the binding of NIVRKKK to Hsc70, possibly by causing a conformational change that masked Hsc70's binding site for the basicpeptide. Two hypotheses are offered to explain the two different peptide motifs. First, it is proposed that Hsc70 recognizes two different amino acid sequence motifs in its dual roles of chaperoning proteins to organelles (NIVRKKK-like sequences) and facilitating protein folding(FYQLALT-like sequences). Second, the NIVRKKK motif may be used to bind certain folded proteins with which Hsc70 interacts, such as itself, p53, and Dnaj2.